Have you thought about running an automated comparison with Arnold (as you blogged at http://openstreetmap.us/2014/12/arnold-for-osm/)? I'd expect that any road showing on Arnold is of reasonable quality; if the corresponding geometry in OSM is tagged with highway=residential, tiger:reviewed=no, that suggests a priority for retagging.

One example I found just by zooming into Eric's Arnold rendering: here in WV there's a highway=residential which has moderate traffic flows and should really be a tertiary.

@jumbanho: Yes, I can see the logic in that. Essentially, as long as unpaved roads are tagged as such, that's great. (What's a little more worrying, and something I've encountered several times, is when people retag these gravel roads as highway=unclassified without adding a surface tag.)

I wonder how you'd tag the short section of the River Cam where boats should follow the left bank, as opposed to the right bank (which is standard everywhere else on the UK waterways). 'driving' doesn't seem the correct word for a boat but maybe I should just let that slide...

The 1%: I don't think it's data consumers who are responsible for this mess. It's tidy-minded people trying to second-guess data consumers. If these tidy-minded people had actually used OSM data they wouldn't be coming up with batshit insane proposals.

At cycle.travel, I suspect I do more detailed analysis (for both routing and display) of paths than any other data consumer. The two most notorious wiki-inspired tags, highway=path and smoothness=, haven't made life any easier for me; they've made it a whole lot more difficult. When highway=path is used without a vast array of supporting tags, which is the case the majority of the time, it's impossible to guess sensible defaults. smoothness= is just a plain bad tag in ways which are too numerous to recite.

Please no! Imports really aren't desperately needed in the US. What's desperately needed in the US is for more people to clean up the disaster area that was the first import of all, TIGER, rather than piling more and more unmaintained, out-dated data on top.

@RobJN: I've considered it but I'm not sure it's appropriate for this task - the amount of corrections to be done to the TIGER data is so vast that, barring a massive upswing in the number of people working on TIGER fixup, that sort of fine-grained approach is unlikely to work. I do wonder whether a P2 vector background layer might be useful, though, in helping to refine geometries.

@kucai: Yes, that's a useful tag and one which the Australians (understandably!) seem to like. It's a little problematic though in that it only addresses the road quality from a car driver's perspective, whereas a surface= tag can be used by cyclists, walkers, horseriders etc.

Essentially it now moves a node, rather than creating a new one, if the nearest point on the existing way happens to be near an existing node. Currently it's "within 15% of the distance to the next node", though I'd like to make that distance-sensitive in due course.

Undelete's pretty unlikely to make a comeback for a while I'm afraid - the way it's implemented in P1 is a bit under-the-radar, and it really needs to become part of the official API first. But you never know...

Would be great to have you along, and congratulations on your edits so far. Do post updates on what you're doing on the diary - other people can help and offer advice. And you never know, if there are tiresome improvement jobs that can equally be done from the aerial imagery, you might be able to get remote assistance for your task.